Method and apparatus for mechanically balancing the disk pack of a hard disk drive

ABSTRACT

The invention includes a method making a balanced disk pack for a hard disk drive, from a disk pack including a spindle motor rigidly coupled, and aligned by at least two open screw holes, with a disk clamp. The invention includes the resulting balanced disk packs, as well as hard disk drives built with such balanced disk packs. The invention also includes apparatus providing the means for implementing the steps of making a balanced disk pack from a disk pack. The invention includes at least one mechanical counterbalance for use in balancing the disk pack of a hard disk drive.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of the priority date of U.S.provisional patent application serial No. 60/413,734, filed Sep. 25,2002, the specification of which is hereby incorporated in its entirety.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION

[0002] The present invention relates to mechanically balancing the diskpack in a hard disk drive.

BACKGROUND INFORMATION

[0003] Hard disk drives contain a plurality of magnetic heads coupled torotating disks. The disk pack rotates the disk surfaces in a hard diskdrive. Imbalances in the disk pack adversely affect communication to andfrom the rotating disk surfaces. Therefore, disk packs must be balancedto minimize rotational variation at the disk surfaces.

[0004] The typical prior art disk pack includes a spindle motor, one ormore disks, possibly one or more spacers, and a disk clamp. Bolts orscrews couple the disk clamp to the spindle motor, acting to clamp thedisk(s) and spacers into a rigidly coupled assembly which is rotated bythe spindle motor during operation.

[0005] Making disk packs includes a rotational balancing process, whichmechanically aligns the disk packs by attaching counterbalances. Atypical balance tolerance for a disk pack is a variation in angularmomentum of 35 milligram-centimeters, as measured by a balancecalibration system.

[0006] There are several existing approaches to balancing disk packsbased upon different counterbalances. These existing approaches havecreated problems, which have added to the cost of production and/ordiminished the reliability of the produced hard disk drives.

[0007] A first prior art balancing approach involves altering asymmetric ring coupled to a disk clamp. Cutting, drilling, or punchingare used to alter the ring.

[0008] A second approach involves drilling one or more holes in eitherthe disk clamp or the spindle motor hub. The spindle motor hub is aspindle motor region containing the screw holes used to couple with thedisk clamp when making the disk pack. Machining holes in the disk clampor the spindle motor hub may introduce contaminants such as machinetailings and machine oils. Furthermore, the machining required isspecific to the particular disk pack and must meet narrow tolerances,making this approach expensive.

[0009] A third approach involves injecting glue and/or heat sealingplastic at selected spots, and in selected amounts, near the disk clampto counterbalance the disk pack. This injection releases contaminants,which require cleaning procedures to restore the cleanliness of the disksystem when assembled. The injected compounds also require a specificenvironment in order to harden correctly, further adding cost, and oftendelays, until the hardening process is completed.

[0010] Accordingly, what is needed are counterbalances, and methods ofbalancing disk packs using such counter balances, which do not requireunit specific machining and which do not create contamination problems.

BRIEF SUMMARY OF THE INVENTION

[0011] The present invention includes methods of making a balanced diskpack from a disk pack that may have previously been unbalanced. Theinvention also includes the balanced disk packs resulting from balancingthe disk packs, as well as the hard disk drives built with such balanceddisk packs. The invention further includes the apparatus making abalanced disk pack from a disk pack.

[0012] The disk pack typically includes a spindle motor rigidly coupledwith a disk clamp, and aligned by at least two open screw holes. Thedisk pack balancing methods use no unit-specific machining operations.Using cleaned counterbalances minimizes contamination, which mayeliminate the cost and production delays of glues and injected plastics.

[0013] The invention includes at least one mechanical counterbalance forbalancing a disk pack. The mechanical counterbalance fits into an openscrew hole, and locks against a locking plate collection member. Thelocking plate collection typically includes the disk clamp and thespindle motor.

[0014] The disk clamp may be the preferred locking plate collectionmember, because if the disk pack with locked mechanical counterbalancesfails to balance, disassembling can salvage at least the spindle motorand disks.

[0015] Preferred mechanical counterbalances include a cylindrical shaftrigidly coupled to a latching assembly and a balance weight. Thecylindrical shaft centers around a primary axis. The latching assemblyincludes a compressible latch rigidly coupled to a latch gap zone. Thebalance head rigidly couples to the latch gap zone. The latchingassembly, including the compressible latch, and the latch gap zone,center around the primary axis.

[0016] The invention includes selecting a counterbalance from acounterbalance type collection of at least two counterbalances withtotal masses, which are different or distinct. Such counterbalances willbe referred to as distinct total masses.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The objects and features of the present invention, which arebelieved to be novel, are set forth with particularity in the appendedclaims. The present invention, both as to its organization and manner ofoperation, together with further objects and advantages, may best beunderstood by reference to the following description, taken inconnection with the accompanying drawings, in which:

[0018]FIG. 1 shows an exploded schematic view of a balanced disk pack ina hard disk drive;

[0019]FIG. 2 shows a side cross-sectional view of the disk pack in thehard disk drive of FIG. 1;

[0020]FIG. 3 shows a perspective view of the disk pack of FIGS. 1 and 2;

[0021]FIG. 4 shows a more detailed view of the cross-section of FIG. 2;

[0022]FIG. 5A shows a top cross-sectional view of a mechanicalcounterbalance of FIGS. 1 to 4;

[0023]FIG. 5B shows a perspective view of the mechanical counterbalanceof FIGS. 1 to 5A;

[0024]FIG. 5C shows a side view of the mechanical counterbalance ofFIGS. 1 to 5B;

[0025]FIG. 5D shows the view along a cut line of the fins of FIG. 5C;

[0026]FIG. 6A shows a top cross-sectional view of a second preferredmechanical counterbalance which could be used in FIGS. 1-4;

[0027]FIG. 6B shows a side view of the second mechanical counterbalanceof FIG. 6A;

[0028]FIG. 6C shows a side cross-sectional view of the second mechanicalcounterbalance of FIGS. 6A-6B;

[0029]FIG. 7 shows an apparatus for making a balanced disk pack from adisk pack;

[0030]FIG. 8 shows a preferred apparatus for making the balanced diskpack as in FIG. 7;

[0031]FIG. 9A shows a detail of the program system of FIG. 8;

[0032]FIG. 9B shows a detail performing the balance operation for theopen screw hole of FIG. 9A;

[0033]FIG. 10A shows a detail selecting a mechanical counterbalance forthe open screw hole of FIG. 9B;

[0034]FIG. 10B shows a detail of inserting the selected counterbalanceinto the open screw hole until the mechanical counterbalance locks intothe open screw hole of FIG. 9B;

[0035]FIG. 11A shows a detail of selecting the mechanical counterbalancefor the open screw hole of FIG. 9B;

[0036]FIG. 11B shows a detail of inserting the selected counterbalanceinto the open screw hole of FIG. 9B;

[0037]FIG. 12A shows of locking the selected counterbalance into theopen screw hole of FIG. 11B;

[0038]FIG. 12B shows further making the balanced disk pack of FIGS. 8and 9A;

[0039]FIG. 13A shows further locking the mechanical counterbalance intothe open screw hole of FIG. 11B;

[0040]FIG. 13B shows further analyzing the disk pack for the balancingoperation for the open screw hole of FIG. 9B.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The following description is provided to enable any personskilled in the art to make and use the invention and sets forth the bestmodes presently contemplated by the inventors for carrying out theinvention. Various modifications, however, will remain readily apparentto those skilled in the art, since the generic principles of the presentinvention have been defined herein.

[0042] The invention includes using at least one mechanicalcounterbalance 100 for balancing a disk pack of a hard disk drive asshown in FIGS. 1 to 4. FIGS. 1 to 4 show a disk pack. A disk packincludes a spindle motor 80 and at least one disk 12 rigidly coupledwith the disk clamp 82. The disk pack is aligned by at least two openscrew holes 85-A and 85-B. Disk packs may further include disk spacers84. Open screw holes 85-A and 85-B are shown only in FIG. 4.

[0043]FIG. 1 shows an exploded schematic view of a hard disk drive 10,including a balanced disk pack employing a preferred mechanicalcounterbalance 100. The hard disk drive 10 also includes the following.A hard disk drive base plate 90, a hard disk drive base 92, a seconddisk 14, separated by a disk spacer 84, a voice coil actuator 30, andthe hard disk drive cover 94.

[0044]FIG. 2 shows a side cross-sectional view of hard disk drive 10with the mechanical counterbalance 100 of FIG. 1 inserted into openscrew hole 85-C of the disk pack, at least partially creating thebalanced disk pack.

[0045]FIG. 3 shows a perspective view of the balanced disk pack of FIGS.1 and 2. Two mechanical counterbalances 100-A and 100-B are insertedinto two open screw holes in disk clamp 82. The Figure also includes adisk ring 86, disk spacer 84, and disk 12.

[0046]FIG. 4 shows a magnified view of a portion of the cross-section ofFIG. 2. The mechanical counterbalance 100 is shown locking against thedisk clamp 82. When fitted into the open screw hole 85-C, the mechanicalcounterbalance 100 aligns with both the disk clamp 82 and the spindlemotor 80.

[0047] The mechanical counterbalance 100, in FIGS. 2 and 4, includesmeans for fitting into the open screw hole, and locking against alocking plate collection member.

[0048] The locking plate collection of FIGS. 1 to 4 includes the diskclamp 82 and the spindle motor 84. The locking plate collection may alsoinclude the disk spacer 84 coupled between the disk clamp 82 and thespindle motor 80.

[0049] Typically, disk spacers do not include screw holes, thus the diskspacers 84, of FIGS. 1 to 4, may or may not include screw holes. In harddisk drives possessing more than one disk, the disk pack furtherincludes one or more additional disk spacers 84, as seen in FIG. 1. Adisk pack may also include disk spacer 84 in hard disk drives using justone disk 12, as in FIGS. 2, 3 and 4.

[0050]FIGS. 5A to 6C show various embodiments of the mechanicalcounterbalances 100 of FIGS. 1 to 4.

[0051] The mechanical counterbalance 100 in FIGS. 5A to 5C includes acompressible latch 130 as a compressible ridge ring. FIGS. 5A, 5B and 5Cshow a top cross-sectional view, a perspective view, and a side view ofthe mechanical counterbalance 100 of FIGS. 1 to 4.

[0052] The mechanical counterbalances 100 of FIGS. 5A to 6C include acylindrical shaft 120 rigidly coupled to a latching assembly 130 to 140and a balance weight 110. The cylindrical shaft 120 is centered around aprimary axis 122. The latching assembly 130 to 140 is also centeredaround primary axis 122. The latching assembly 130 to 140 includes acompressible latch 130 rigidly coupled to latch gap zone 140. Thebalance head 110 rigidly couples to the latch gap zone 140.

[0053] The compressible latch 130 in FIGS. 5D to 6C is a ring of threecompressible fins. FIG. 5D shows the view along cut line 102, of FIG.5C, for the fins 132, 134, and 136. FIGS. 6A, 6B and 6C show topcross-sectional, side, and side cross-sectional views of a preferredmechanical counterbalance 100. The compressible latch 130 may includetwo or more fins.

[0054] The mechanical counterbalance 100 of FIGS. 5A to 6C may beprimarily composed of one material formed into the cylindrical shaft120, the latching assembly 130 to 140 and the balance weight 110. Thematerial may essentially be a castable material, such as plastic. Theplastic may preferably be a version of nylon. In alternate embodiments,the counterbalance 100 maybe formed of several different materials.

[0055] The mechanical counterbalance 100 may preferably be free ofcontaminants. Example contaminants include a particle larger than afirst specification, a hanging burr larger than a second specification,and a contaminant determined by a third specification. Each of thesespecifications is derived from a reliability specification used in themanufacturing of the hard disk drive.

[0056] The balance weight 110 of FIGS. 5A to 6C includes an interiorface 112, exterior face 114, and side faces 116 and 118.

[0057] Mechanical counterbalance 100 has a total mass at essentially theprimary axis 122 (FIGS. 5A, 5B, 6A, and 6B) when balancing the diskpack. Mechanical counterbalance 100 preferably balances the disk pack byfitting the primary axis 122 through the center of the open screw hole85-C.

[0058] As in FIGS. 2 and 3, the following occurs when inserting themechanical counterbalance 100 of FIGS. 5A to 6C into an open screw holeof the disk pack. The cylindrical shaft 120 fits into the open screwhole. The compressible latch compresses while passing through the screwhole, and expands after passing through the screw hole to lock themechanical counterbalance 100 against a locking plate collection member.

[0059] FIGS. 5A-6C also show the following. The means 120 for fittingmechanical counterbalance 100 into at least one open screw hole 85. Themeans for locking mechanical counterbalance 100 into the open screw holeagainst a locking plate collection member, after fitting mechanicalcounterbalance 100 into the open screw hole 85. The means for lockingincludes the compressible latch 130, the latch gap zone 140, and thebalance head 110.

[0060]FIGS. 7 and 8 show two embodiments supporting the invention'sbalancing method for disk packs.

[0061] The invention includes a method of balancing a disk packinvolving selecting a mechanical counterbalance from a counterbalancetype collection. The counterbalance type collection comprises at leasttwo counterbalances, each with a distinct total mass. In experiments bythe inventors, two counterbalances had total, preferred masses of about24 mg and 54 mg.

[0062]FIG. 7 shows an apparatus for making a balanced disk pack 420 froma disk pack 410. The disk pack 410 includes a spindle motor 80 rigidlycoupled with a disk clamp 82. The spindle motor 80 aligns with the diskclamp 82 by at least two, and preferably four, open screw holes 85-A to85-D.

[0063]FIG. 8 shows a preferred apparatus for making a balanced disk pack420 from a disk pack 410 as in FIG. 7. The method uses an assemblyworkstation 400 controlled by a computer executing a program system 530of program steps residing in memory 520.

[0064] The mechanical counterbalance mass collection 450 includes atleast two members 460 and 462. The mechanical counterbalance masscollection members are the distinct total masses of the types 480 and482 of the mechanical counterbalance type collection, as in FIGS. 7 and8.

[0065] As shown in FIG. 7, arrows 324 and 422 preferably represent meansfor inserting the selected counterbalance 102 into the screw hole.

[0066] Discussion of making balanced disk packs hereafter will be interms of the flowcharts of program system 530 of FIG. 8. This simplifiesthe discussion, and is not meant to limit the scope of the claims. FIGS.9A to 13B show the method of balancing a disk pack, using theinvention's mechanical counterbalance.

[0067] The following flowcharts of the methods of the invention possessarrows with reference numbers. These arrows signify flow of control, andsometimes data. The arrows support implementations including at leastone program step, or program thread, executing upon a computer,inferential links in an inferential engine, state transitions in afinite state machine, or learned responses within a neural network.

[0068] The operation of starting a flowchart refers to at least one ofthe following. Starting may refer to entering a subroutine in a macroinstruction sequence in a computer. Starting may refer to entering intoa deeper node of an inferential graph. Starting may refer to directing astate transition in a finite state machine, possibly while pushing areturn state. Starting may refer to triggering a collection of neuronsin a neural network.

[0069] The operation of termination in a flowchart refers to thecompletion of operations. It may result in a subroutine return,traversal to a higher node in an inferential graph, popping of apreviously stored state in a finite state machine, and/or return todormancy of firing neurons in a neural network.

[0070] A computer as used herein will include, but is not limited to, aninstruction processor. The instruction processor includes at least oneinstruction processing element and at least one data processing element,each data processing element controlled by at least one of theinstruction processing elements.

[0071]FIG. 9A shows a program system 530 of FIG. 8 for making thebalanced disk pack 420 from the disk pack 410, for each of the openscrew holes 85. Operation 1002 analyzes the disk pack 410 for abalancing operation for the open screw hole. Operation 1012 performs thebalance operation for the open screw hole.

[0072]FIG. 9B shows a detail of operation 1012 of FIG. 9A, if a balanceaction is determined for the open screw hole. Operation 1032 selects amechanical counterbalance for the open screw hole to create a selectedcounterbalance 102 of a total mass. Operation 1042 inserts the selectedcounterbalance 102 into the open screw hole, until the selectedcounterbalance locks into the open screw hole, at least partiallycreating the balanced disk pack.

[0073]FIGS. 10A and 10B show one of several possible, equivalentimplementations of the operations of FIG. 9B, including implementationswith a shared test.

[0074]FIG. 10A shows a detail of operation 1032 of FIG. 9B. Operation1132 determines if a balance action is needed for the open screw hole.When the determination 1134 is Yes, operation 1136 selects a mechanicalcounterbalance for the open screw hole to create a selectedcounterbalance 102 of a total mass.

[0075]FIG. 10B shows a detail of operation 1042 of FIG. 9B. Operation1152 determines whether the open screw hole needs a balance action. Whenthe determination 1154 is Yes, operation 1156 inserts the selectedcounterbalance 102 into the open screw hole until the selectedcounterbalance 102 locks into the open screw hole at least partiallycreating the balanced disk pack.

[0076]FIG. 11A shows a detail of operation 1032 of FIG. 9B. Operation1172 selects the mechanical counterbalance for the open screw hole fromthe counterbalance collection 470 and from the counterbalance masscollection 450, creating the selected counterbalance 102 with the totalmass, as shown in FIGS. 8 and 9.

[0077] In FIGS. 7 to 11A, the selected counterbalance 102 is an instanceof a member of the mechanical counterbalance collection 470.

[0078] The arrows in FIGS. 7 and 8 pointing to and pointing from theselected counterbalance 102 preferably represent assembly feedmechanisms.

[0079]FIG. 11B shows a detail of operation 1042 of FIG. 9B. Operation1192 fits the selected counterbalance 102 into the open screw hole.Operation 1202 locks the selected counterbalance 102 into the open screwhole against a locking plate collection member, after fitting theselected counterbalance into the open screw hole.

[0080]FIG. 12A shows a detail of operation 1202 of FIG. 11B. Operation1202 locks the selected counterbalance 102 into the open screw holeagainst the disk clamp after fitting the selected counterbalance intothe open screw hole.

[0081]FIG. 12B shows a detail of program system 530 of FIGS. 8 and 9Aproviding, if the disk pack fails to balance, disassembly of the diskpack with fitted counterbalances to salvage at least the spindle motorand the disks. This is performed as follows. Operation 1242 confirms abalance failure for the disk pack. Operation 1252 removes the diskclamp, and all of the mechanical counterbalances locked to the diskclamp, from the disk pack to create a partial disk pack. Operation 1262then rigidly couples a second disk clamp to the spindle motor of thepartial disk pack, and aligns it by open screw holes, to recreate thedisk pack.

[0082]FIG. 13A shows a detail of operation 1202 of FIG. 11B. Operation1302 compresses a compressible latch into the open screw hole. Operation1312 expands this latch after to compressing it into the open screw holeto lock the mechanical counterbalance against the locking platecollection member.

[0083]FIG. 13B shows a detail of operation 1002 of FIG. 9B. Operation1352 uses a disk pack balance instrument 304 of FIG. 8 to analyze thedisk pack 410 for the balancing operation. Hoffman manufactures thepreferred disk pack balance instruments.

[0084] Those skilled in the art will appreciate that various adaptationsand modifications of the just-described preferred embodiments can beconfigured without departing from the scope and spirit of the invention.Therefore, it is to be understood that, within the scope of the appendedclaims, the invention may be practiced other than as specificallydescribed herein.

What is claimed is:
 1. At least one mechanical counterbalance for use inbalancing a disk pack that includes a spindle motor rigidly coupled andaligned by at least two open screw holes with a disk clamp, comprising:a locking plate collection comprising a disk clamp and a spindle motor acylindrical shaft rigidly coupled to a latching assembly, both centeredaround a primary axis, and a balance weight; wherein said latchingassembly includes a compressible latch rigidly coupled to a latch gapzone, both centered around said primary axis; wherein said balance headis rigidly coupled to said latch gap zone; wherein said cylindricalshaft is rigidly coupled to said compressible latch; wherein for each ofsaid open screw holes, when said mechanical counterbalance is insertedinto said open screw hole to lock said mechanical counterbalance, saidcylindrical shaft fits into said open screw hole, said compressiblelatch compresses while passing through said disk clamp; and saidcompressible latch expands after passing through said disk clamp;wherein said mechanical counterbalance has a total mass provided atessentially said primary axis when used in said disk pack.
 2. Theapparatus of claim 1, wherein said mechanical counterbalance isprimarily composed of one material formed into said cylindrical shaft,said latching assembly and said balance weight; wherein said material isat least one member of the collection comprising said material isessentially a plastic, and said material is castable.
 3. The apparatusof claim 2, wherein said plastic is a nylon.
 4. The apparatus of claim1, wherein said mechanical counterbalance is free of each member of acontaminant collection comprising a particle larger than a firstspecification, a hanging burr larger than a second specification, and acontaminant determined by a third specification; wherein each of saidfirst specification, said second specification, and said thirdspecification, is derived from a reliability specification used in themanufacturing said hard disk drive.
 5. The apparatus of claim 1, whereinsaid mechanical counterbalance locks against said disk clamp.
 6. Theapparatus of claim 1, said locking plate collection further comprisingat least one of said disk spacers.
 7. The apparatus of claim 1, whereinsaid compressible latch includes at least one member of a latchcollection comprising a compressible ridge ring, and an M compressiblefin ring; wherein M is at least two.
 8. A method of making a balanceddisk pack, for a hard disk drive, from a disk pack including a spindlemotor rigidly coupled, and aligned by at least two open screw holes,with a disk clamp, wherein said method comprises, for each of said openscrew holes, of the steps of: analyzing said disk pack for a balancingoperation for said open screw hole; performing said balance operationfor said open screw hole, further comprising said steps of: selecting amechanical counterbalance for said open screw hole to create a selectedcounterbalance of a total mass, if a balance action is determined forsaid open screw hole; and inserting said selected counterbalance intosaid open screw hole until said mechanical counterbalance locks intosaid open screw hole to at least partially create said balanced diskpack, if said balance action is determined for said open screw hole. 9.The method of claim 8, wherein the step selecting said mechanicalcounterbalance for said open screw hole further comprising the step of:selecting said mechanical counterbalance for said open screw hole from acounterbalance collection and from a counterbalance mass collection tocreate said selected counterbalance with said total mass; wherein saidmechanical counterbalance mass collection comprising at least twomembers; wherein said total mass is a member of said mechanicalcounterbalance mass collection; wherein each of said members of saidmechanical counterbalance mass collection approximates the total mass ofat least one member of said mechanical counterbalance collection; andsaid selected counterbalance is an instance of a member of saidmechanical counterbalance collection.
 10. The method of claim 8, whereinthe step inserting said selected counterbalance into said open screwhole further comprising the steps of: fitting said selectedcounterbalance into said open screw hole; and locking said selectedcounterbalance into said open screw hole against a member of a lockingplate collection after fitting said selected counterbalance into saidopen screw hole; wherein said locking plate collection comprising saiddisk clamp and said spindle motor.
 11. The method of claim 10, whereinthe step locking said mechanical counterbalance into said open screwhole further comprising the steps of: compressing a compressible latchin said open screw hole; and expanding said compressible latch aftercompressing said compressible latch in said open screw hole to lock saidmechanical counterbalance against said locking plate collection member.12. The method of claim 11, wherein said compressible latch includes atleast one member of a latch collection comprising a compressible ridgering, and an M compressible fin ring; wherein M is at least two.
 13. Themethod of claim 10, wherein said locking plate collection furthercomprising at least one disk spacer.
 14. The method of claim 10, whereinthe step locking said selected counterbalance into said open screw holefurther comprising the step of: locking said selected counterbalanceinto said open screw hole against said disk clamp after fitting saidmechanical counterbalance into said open screw hole; wherein said methodfurther comprising the steps of: confirming a balance failure of saiddisk pack after locking said mechanical counterbalance; removing saiddisk clamp and all of said mechanical counterbalances locked to saiddisk clamp to create a partial disk pack; and rigidly coupling a seconddisk clamp to said spindle motor of said partial disk pack, and aligningby said open screw holes, to recreate said disk pack.
 15. The method ofclaim 8, wherein the step analyzing said disk pack for said balancingoperation for said open screw hole further comprising the step of: usinga disk pack balance instrument to analyze said disk pack for saidbalancing operation.
 16. Said balanced disk pack as a product of theprocess of claim
 8. 17. A method of making a hard disk drive, comprisingthe step of: using said balanced disk pack of claim 16 to create saidhard disk drive.
 18. Said hard disk drive as a product of the process ofclaim
 17. 19. An apparatus operating upon said disk pack to create saidbalanced disk pack, comprising, for each of said steps of claim 8, themeans for implementing said step.
 20. The apparatus of claim 19, whereinat least one of said means is implemented using at least one member ofthe collection comprising an assembly workstation, a computercontrolling at least part of said assembly workstation, a memoryaccessibly coupled with said computer, a program step residing in saidmemory to direct said computer in implementing said means, a finitestate machine controlling at least part of said assembly workstation.21. Said mechanical counterbalance of claim 8, comprising, for at leastone of said open screw holes, of: means for inserting said mechanicalcounterbalance into said open screw hole until said mechanicalcounterbalance locks into said open screw hole, further comprising:means for fitting said mechanical counterbalance into said open screwhole; means for locking said mechanical counterbalance into said openscrew hole against a member of a locking plate collection after fittingsaid selected counterbalance into said open screw hole; wherein saidmechanical counterbalance has a total mass provided at essentially saidprimary axis when used in said disk pack.
 22. The apparatus of claim 21,wherein said mechanical counterbalance is primarily composed of onematerial forming said means; wherein said material is at least onemember of the collection comprising said material is essentially aplastic, and said material is castable.
 23. The apparatus of claim 22,wherein said plastic is a nylon.
 24. The apparatus of claim 21, whereinthe means for locking said mechanical counterbalance into said openscrew hole against said locking plate collection member after fittingsaid selected counterbalance into said open screw hole furthercomprising: means for compressing a compressible latch in said openscrew hole, and means for expanding said compressible latch aftercompressing said compressible latch in said open screw hole to lock saidmechanical counterbalance against said locking plate collection member.25. The apparatus of claim 24, wherein said compressible latch includesat least one member of a latch collection comprising a compressibleridge ring, and an M compressible fin ring; wherein M is at least two.26. The apparatus of claim 21, wherein said mechanical counterbalance isfree of each member of a contaminant collection comprising a particlelarger than a first specification, a hanging burr larger than a secondspecification, and a contaminant determined by a third specification;wherein each of said first specification, said second specification, andsaid third specification, is derived from a reliability specificationused in the manufacturing said hard disk drive.
 27. The apparatus ofclaim 21, wherein said mechanical counterbalance locks against said diskclamp.
 28. The apparatus of claim 21, wherein said locking platecollection further comprising at least one of said disk spacers.